An echelon diffraction grating which has excellent heat resistance and can be produced at a low cost and an optical waveguide which has high heat resistance, small absorption of a communication wavelength of a near infrared range, and satisfies reliability and a low loss at an optical communication range. The echelon diffraction grating comprises a substrate, and an organopolysiloxane film having a maximum thickness of 1 &mgr;m to 1 mm formed on the surface of the substrate and has a plurality of steps having a predetermined width of 1 to 500 &mgr;m and a predetermined height of 5 to 500 &mgr;m formed on the organopolysiloxane film, and the organopolysiloxane film contains dimethylsiloxane and phenyl(or substituted phenyl)siloxane as essential ingredients.